In this paper we discuss the test results for concretes containing various amounts of ggbs as compared to concretes made with Portland cement. The main objective of these tests is to evaluate the influence of varying air content in such mixtures on the structure and frost resistance of concrete. The authors suggest that the approach presented here allows for a safe design of concrete mixtures in terms of their frost resistance.

The results indicate that concrete can be resistant to surface scaling even at the W/C ratio markedly higher than 0.45. Increased addition of ggbs leads to a decrease in concrete resistance to surface scaling. Proper air entrainment is the fundamental factor for frost-resistant concrete, and the air void system has to be assessed (micropore content A₃₀₀, spacing factor L). The addition of ggbs increases pore diameters, thus, to obtain the appropriate air pore spacing factor, micropore quantities introduced have to be increased.

The effect of the air-entraining agent on properties of mortar mixtures as well as on the compressive strength of hardened mortars was the objective of this study. Such mortars contain a certain amount of evenly spread closed air-voids pores with dimensions of 0.02-0.05 mm. On the one hand, the presence of a large volume of such air bubbles results in the reduction of mechanical properties of mortar. On the other hand, the use of this technological approach improves rheological properties of mortar mixture. The effect of the air entrainment on the flow, density, volume of entrained air of mortar mixture and compressive strength of hardened mortar was established. Obtained results show substantial increasing in the mortar flow at cement to sand ratio 1:2 by 1.8 times. The further decrease of C:S ratio results in a slight increase of the flow and even negligible its decrease at C:S = 1:4 compared to the reference mortar. The increase of the volume of entrained air results in the decrease of the density and compressive strength of mortar, but improve the resistance to freezing/thawing cycles. The results of this study can be a guide for mortar mix design to choose the most appropriate mix proportion to produce economically efficient mortars.

Every change in the bottle geometry aswell as every change of physical and rheological properties poses a risk of excessive gas entrainment during a filling process. To maintain satisfactory filling efficiency there is a need to optimise this process with respect to all adverse phenomena which affect the fluid flow, such as spluttering on the bottom, air caverns formation and air entrainment with incoming liquid. This paper comprises numerical simulations of two filling methods. The first method involves dosing with a pipe placed over the free liquid surface of a fully filled bottle. The second method covers filling with a pipe located near the bottom. Moreover, the influence of rheological properties and surface tension values is considered. The comprehensive analysis of amount of entrained air represented by air volume fraction in dispensed liquid let the authors define the influence of filling speed on the mechanism and amount of entrapped air.

Incorporation of air-entraining agent has improved recycled concrete freeze-proof durability. However, it is very lacking to study the role of the entraining agent. In this paper, the influence of an air-entraining agent on freeze-proof durability for the ordinary C30 recycled coarse aggregate (RCA) concrete and air-entrained C30 RCA concrete was investigated with the laboratory comparative tests. The mass loss, the dynamic modulus of elasticity, ultrasonic wave velocity and cubic compressive strength were measured during freeze-thaw cycles. The test result showed the concrete’s performance was similar to the ordinary concrete and was better than that of other recycled concretes when the content of RCA was 50% and 0.03% of air-entraining agent was added for C30 RCA concrete. Meanwhile, the addition of air-entraining agent has an improved effect on the performance of recycled concrete, but the effect was limited.